Percutaneous transluminal coronary angioplasty (PTCA) is used to increase the lumen diameter of a coronary artery partially or totally obstructed by a build-up of cholesterol fats or atherosclerotic plaque. Typically a first guidewire of about 0.038 inches in diameter is steered-through the vascular system to the site of therapy. A guiding catheter, for example, can then be advanced over the first guidewire to a point just proximal of the stenosis. The first guidewire is then removed. A balloon catheter on a smaller 0.014 inch diameter second guidewire is advanced within the guiding catheter to a point just proximal of the stenosis. The second guidewire is advanced into the stenosis, followed by the balloon on the distal end of the catheter. The balloon is inflated causing the site of the stenosis to widen. The dilatation of the occlusion, however, can form flaps, fissures and dissections which threaten reclosure of the dilated vessel or even perforations in the vessel wall.
Although the dimensions in the above example are suited to the coronary arteries, any body lumen can be treated by percutaneous transluminal angioplasty (PTA), including the vas deferens, ducts of the gallbladder, prostate gland, trachea, bronchus and liver. The body lumens range in diameter from small coronary vessels of 3 mm or less to 28 mm in the aortic vessel. The invention applies to acute and chronic closure or reclosure of body lumens.
It is advantageous for catheter shafts to have a stiff proximal end for pushability and a more flexible distal end for better tracking through tortuous lesions. Abutting stiff tubular materials to more flexible tubular materials results in a point at which kinking can occur. What is needed is a transition area therebetween to provide a smooth transition between the stiff proximal section and the more flexible section of the catheter shaft and thereby reduce kinking.
U.S. Pat. No. 4,960,410 to Pinchuk for "Flexible Tubular Member for Catheter Construction" discloses a spirally cut tubular member which extends through the balloon to the distal end of the catheter. The tubular member includes a first relatively stiff tube that is spirally cut along a distal portion and also includes a second more flexible tube that covers the spirally cut distal portion of the stiff tube to make a distal portion of the tubular member more flexible than a proximal portion of the elongated tubular member.
U.S. Pat. No. 5,599,326 to Carter for "Catheter with Multi-Layer Section" discloses an interior stiffener comprising a spirally cut tube member and an exterior tube member.